Composition and temperature-dependent computations of structural correlations and mass transport in liquid Au-Ge alloys.

The temperature and composition-dependent structural and transport properties of Au-Ge liquid alloys are investigated using a hard-sphere reference system with square-well attractive interactions between the particles. The optimized square-well parameters generate static structure factors and the main peak features of the total radial distribution functions that are in good agreement with the experimental values, over the investigated composition and temperature range, along with the coordination numbers, which are in good conformity with the available ab initio molecular dynamic (AIMD) results. Furthermore, the mutual diffusion coefficients evaluated from the computed structural correlations are also consistent with the available experimental values. The analysis shows that increasing Ge concentration does not significantly change the nearest neighbour separation, but modifies the local packing efficiency leading to a nonmonotonic variation of the coordination numbers. The long-wavelength density fluctuation and isothermal compressibility exhibit maximum values at 40 atomic percent Ge, indicating enhanced collective density fluctuations at intermediate compositions. The long wavelength concentration fluctuation, SCC(0), remains below the ideal value over the entire composition range, confirming persistent chemical short-range order that becomes strongest at equi-atomic composition and weakens with increasing temperature. The calculated self and mutual diffusion coefficients follow Arrhenius temperature dependence, which is consistent with the reported experimental and AIMD studies for the given range of temperatures, providing a consistent structural basis for understanding interdiffusion in liquid Au-Ge alloys.